Representative George Miller, a California Democrat who spent four decades as one of the top liberal legislators in the House, announced Monday that he will not seek reelection this fall.

A close ally of House Democratic leader Nancy Pelosi, Miller has represented a swath of the East Bay of the San Francisco area since 1975. The chairman of three committees during his stint on Capitol Hill, Miller worked with Republicans to pass the No Child Left Behind education overhaul in 2002 and helped usher President Barack Obama’s health care reform law through the House in 2009. The liberal magazine The Nation named him the “most valuable” member of the House last year in recognition of his work on issues such as minimum wage, workers’ rights and food stamps.

“I’m proud of what I have been able to accomplish on behalf of children, working people and the environment, in my district and for our country, especially passage of national health care reform,” Miller said in a statement released by his office. “Now, I look forward to one last year in Congress fighting the good fight.”

For much of his time on the Hill, Miller was also known for living in a Capitol Hill townhouse with fellow Democratic lawmakers like Senators Chuck Schumer and Dick Durbin—an arrangement that formed the basis for Amazon series Alpha House. “Seeking roommate. 20 terms in the House & unmatched legislative record preferred. Lover of cold cereal a must,” Schumer tweeted.

Miller, 68, will retire at the end of the year. While his district is unlikely to slip into Republican hands, his is the latest in a spate of Democrat retirements that have only lengthened the party’s long odds of retaking the lower chamber in November’s midterm elections.